Suspension system for a bicycle

Abstract

A bicycle frame assembly includes a main frame portion having a steering tube at its forward end and a pedal crankset bracket at its rearward end. An intermediate frame portion is pivotably connected to the main frame portion near the steering tube and extends rearwardly therefrom to a seat tube. A rear frame portion includes a pair of upper arm members and a pair of lower arm members connected at distal ends defining a pair of rear wheel drop outs. The upper arm members angle diagonally upwardly and are connected to the intermediate frame portion through a shock absorber. The lower arm members connect through a first link assembly to a main pivot point provided on the main frame portion above and in closely spaced relation to the crankset bracket. The first link assembly extends forwardly and upwardly from the main pivot point and defines another pivot point for connection to a frame member extending downwardly as part of the intermediate frame portion. A second link assembly fixedly attached to the upper ends of the upper arm members pivotably connects at the upper pivot point of the first link assembly and the downwardly directed member of the intermediate frame portion. By the foregoing arrangement, a rear wheel suspension system is provided in which the bicycle has substantial vertical compliance but relatively high lateral stiffness. Also, the frame may, at the same time, be constructed of relatively lightweight tubular members. Further, with the main pivot point aligned proximate the top portion of the drive chain, differential pedal forces as the suspension system is active are minimized.